Hello coroutine community :wave: I’ve just update...

# coroutines

[Florent Dambreville]

Hello coroutine community 👋

I’ve just updated my kotlin version to 1.6.20 and I get a crash when calling a suspendCoroutine function :

var topupCountries: Deferred<Set<String>> = buildCountriesAsync()
    private set

private fun buildCountriesAsync() = CoroutineScope(backgroundDispatcher).async(start = CoroutineStart.LAZY) {
    getCountries()
}



private suspend fun getCountries(): Set<String> {
    return try {
        topupCountries.getCompleted()
    } catch (exception: IllegalStateException) {
    
        // Crash here
        fetchRestrictedTopupCountries()
    } }

private suspend fun fetchRestrictedTopupCountries(): Set<String> {
    return suspendCoroutine { continuation ->
        val request = ApiTopupRequestFactory.getTopupCountries(
            listener = {
                val setResult = it.countries.toSet()
                continuation.resume(setResult)
            },
            errorListener = {
                continuation.resume(setOf())
            }
        )
        execute(request)
    }
}

The error is : java.lang.ClassCastException: kotlin.coroutines.intrinsics.CoroutineSingletons cannot be cast to java.util.Set

Am I doing something wrong here ? Anyone else with this issue ?

[Florent Dambreville]

After some research, I found a similar problem back in 2019 : https://github.com/Kotlin/kotlinx.coroutines/issues/1091

[Florent Dambreville]

It seems the issue comes from the inline and crossinline usage

[Florent Dambreville]

Indeed the suspendCoroutine uses thoses two :
suspend inline fun <T> suspendCoroutine(
crossinline block: (Continuation<T>) -> Unit
): T

[Florent Dambreville]

Just read that the getCompleted function is not meant to be used like that